With the continuous growth of the Internet scale, a great variety of network services and advanced multimedia systems emerged. Since real-time services are sensitive to network transmission delay and delay dithering, etc., they may be affected considerably when a bursty File Transport Protocol (FTP) service or a Hypertext Transport Protocol (HTTP) service involving image files appears on the network. Furthermore, multimedia services occupy a large bandwidth, and consequently, a reliable transmission for key services may be difficult to be ensured by the existing networks.
In view of the above, various Quality of Service (QoS) technologies have emerged as desired. The IETF (Internet Engineering Task Force) have recommended various service models and mechanisms to meet the demand of QoS. At present, it has been widely accepted by the industry that Integrated Service (Int-Serv) model may be used for the access and the edge of a network, and Differentiated Service (Diff-Serv) model may be used for the core of the network.
Since the Diff-Serv model only provides a measure for priority-guaranteed QoS, its actual effect may be unpredictable regardless of its high utilization of wire lines. For this reason, the industry has introduced an independent bearer control layer for differentiated services of a backbone network, and established a set of special Diff-Serv QoS signaling mechanisms. In order to propel applications of Diff-Serv, a QoS test network for the Diff-Serv model, i.e. a QBone test network, promoted by IETF together with some manufacturers and research institutes, has used a Bandwidth Broker model to realize a network resource and topology management, and some other manufacturers have proposed similar QoS server/resource manager technologies to manage topology resources and to coordinate QoS capabilities of respective Diff-Serv regions.
The above methods each establish a resource management layer for a Diff-Serv network to manage topology resources of the network. Since the traditional definition of Diff-Serv has some limitations, the above Diff-Serv model for the resource management may be referred to as a network model with an independent bearer control layer (or a centralized resource control layer) to avoid confusion.
In such a network model with an independent bearer control layer, as illustrated in FIG. 1, a bearer network control server including a Bandwidth Broker or a QoS server/resource manager may be configured with a management rule and network topology, and may allocate resource in response to a service bandwidth request from a user. Information, such as the service bandwidth request from the user, a result of the request, information of a path allocated for the service request by the bearer network resource manager and the like, may be transmitted via signaling among the bearer network control servers of each management domain.
When the bearer control layer handles the service bandwidth request from the user, the path for a user service may be determined, and the bearer network resource manager may notify an edge router to forward a service stream through the designated path.
As to how the bearer network implements forwarding the user service stream through a designated route in accordance with the path determined by the bearer control layer, a primary technology existing in the industry is the Multi-protocol Label Switching (MPLS) technology, which may establish a Label Switched Path (LSP) along the service stream path designated by the bearer control layer using a Resource Reservation, and may establish an end-to-end LSP using the Resource Reservation Protocol-Traffic Engineering (RSVP-TE) or an explicit routing mechanism of the Constraint-Routing Label Distribution Protocol (CR-LDP).
The above methods may entirely guarantee an end-to-end QoS as required by services, but all telecommunication services have to be processed equally according to the above solutions. In other words, a call may be admitted when the resources are adequate, but may be rejected or provided with a degraded QoS when the resources are inadequate. However, some emergency calls in the network require to be admitted unconditionally and without any QoS-degrading no matter how the network status is, for example, 110 (police call), 119 (fire call), 120 (ambulance call) or other emergency calls. If the emergency calls are treated without differentiation, the emergency services may not be handled when the resources are insufficient, which may cause great loss of lives and belongings, or major accidents.
However, no satisfied solution has so far been proposed for handling emergency services in the network on the independent bearer control layer. As a result, it would be difficult to meet the specific demand of emergency services.